1. Field of the Invention
The present invention relates to a terminal crimping method and a crimp terminal used therefor.
2. Description of the Related Art
As one of the crimp terminals crimped on an end of an electric wire, an opened barrel type crimp terminal 90 shown in FIG. 1 has been conventionally known. The crimp terminal 90 comprises a pair of barrel portions. The barrel portions are, respectively, a wire barrel portion crimped on a conductor W1 of an electric wire W and an insulation barrel portion crimped on an insulated end W2 of the electric wire W.
The wire barrel portion includes: a body 900 of semicircular cross section which surrounds the conductor W1 of the electric wire W; and a pair of claws 91a and 91b integrally extended from ends of a circular arc of the body 900 and adapted to be crimped on the conductor W1. The insulation barrel portion includes claws 92a and 92b integrally extended from a portion of the body 900 which contains the insulated end W2 of the electric wire W and is adapted to be crimped on the insulated end W2.
In crimping the barrel portions of the crimp terminal 90, crimpers 93 and anvils 94 are used. Specifically, the conductor W1 and the insulated end W2 are respectively introduced into the body 900 of the barrel portions. The barrel portions are put between the two pairs of crimpers 93 and anvils 94 which are opposed to each other in the vertical direction. After that, the crimpers 93 are lowered to crimp the claws 91a, 92a, 91b and 92b between the crimpers 93 and the anvils 94, to thereby crimp the terminal 90 on the end of the electric wire W.
As shown in FIG. 2, in a crimping method for the claws 91a and 91b composing the wire barrel portion, a so-called F-crimp type terminal would be used having claws 91a and 91b cutting into the conductor W1 of the electric wire W while contacting respective tip ends of the claws 91a and 91b with each other.
In such a F-crimp type terminal, both claws 91a and 91b are sufficiently bent. Claw 91a and claw 91b symmetrically contact each other at the center of the wire barrel portion, thereby making it possible to obtain high reliability of crimping. As shown in FIG. 3, however; the smaller the crimp width d or the width of the wire barrel portion in a crimp terminal due to a thin electric wire W, then the larger the wall thickness t of the claws 91a and 91b relative to the electric wire W. If such a wire barrel portion is crimped, the claws 91a and 91b may not be bent as calculated. For example, the claw 91b may collide with the claw 91a. This insufficient bending of the claws 91a and 91b can result in inferior reliability of crimping because the claws 91a and 91b would easily separate due to thermal expansion in use or the like.
As shown in FIG. 4 and FIGS. 5A to 5C, there is proposed a so-called overlap crimping terminal having a pair of claws 91a and 91b on the wire barrel portion that overlap one another (for example, Japanese Patent Unexamined Publication No. 3-165478).
A crimper 93 used for this overlap crimping terminal has first and second round surfaces 93c and 93d so smoothly connected with each other so as to provide a step 93b therebetween. Both surfaces 93c and 93d form an innermost portion of a notched groove 93a into which the claws 91a and 91b are introduced (see FIG. 4). Cooperating with an anvil 94, this crimper 93 pushes the wire barrel portion interposed between the crimper 93 and the anvil 94. In this operation, the one claw 91a and the other claw 91b are respectively located along the corresponding first and second round surfaces 93c and 93d, so that one claw 91a laps over the other claw 91b by the step 93b between the round surfaces 93c and 93d.
The foregoing overlap crimping terminal enhances the reliability of crimping better than that of an F-crimp type terminal. Nevertheless, even the claws 91a and 91b of this overlap crimping terminal may collide in the case of a crimp terminal 90 having a small width d (see FIG. 5C).
The reason for this is that the claws 91a and 91b of the crimp terminal 90 introduced into the notched groove 93a of the crimper 93 meet with each other when the claws 91a and 91b contact with the first round surface 93c (see FIG. 5A), and the crimping operation of the crimp terminal 90 progresses without releasing the contacting state (see FIGS. 5B and 5C). Because such contacting claws 91a and 91b are hard to overlap, both sides of the wire barrel portion are fractured, so that wrinkled cracks X are produced. In addition, the claws 91a and 91b can not overlap, so that a crimped portion of the crimp terminal 90 tends to be opened.
Accordingly, what is really needed is a terminal crimping method and a crimp terminal used therefor in which overlap crimping can be reliably carried out.